The present invention relates to mechanical tube expanders of the type in which a trunkated polyhedral pyramid is provided as basic support, and tube expanding segments are disposed for sliding on the surfaces of the pyramid.
Tube expanders of the type referred to above are known in different varieties. One type, for example, is shown in U.S. Pat. No. 3,798,955. Another type is shown in German Pat. No. 2,258,360. The latter expander has T-shaped guide elements for positioning and guiding the expander segments. The segments have rectangular glide portions respectively running in undercut rails of the guide elements. In this known construction, the guide elements are disposed on the corner edges of the polyhedral pyramid and fastened thereto by bolts. It was found that these bolts may readily loosen and may project into the gap between two segments which narrows when the segments are shifted towards the narrow end of the pyramid. Thus, such bolts may be wedged into that gap and break the expander.